The present invention relates to an absorber which is provided within the cover pad above the boss plate in the boss portion of a vehicle steering wheel in order to absorb impact energy when impact is applied to the cover pad and, more particularly, to a shock energy absorber composed of a thin metal sheet.
Impact absorbers of this kind are generally composed of a metal sheet which is bent into a U-shaped configuration and disposed between a cover pad and a boss plate. When an impact load is applied to the cover pad, the impact absorber is buckled to absorb the impact energy.
However, in order to absorb impact energy solely by means of such an impact energy absorber, it is necessary to make the absorber have at least a certain minimum thickness which fact makes it difficult to reduce the steering wheel in weight. Referring to FIG. 1 to solve this problem, it has previously been proposed that the deformation of a cover pad 3 itself and the interference action between the cover pad 3 and an impact energy absorber 4 also be utilized for absorption of impact energy when an impact load is applied, thereby reducing the impact energy absorber in thickness and weight, as shown in FIG. 1.(See Japanese Utility Laid-Open No. 143766/1983).
The impact energy absorber 4 is disposed within substantially square box-shaped cover pad 3 in a boss portion 1, and has, as a conventional absorber, an upper plate 4a provided along the inner wall of the upper portion 3a of the cover pad 3 and side plates 4b and 4c which are bent downward from both ends of the upper plate 4a such as to be disposed along the inner wall of the side portion 3B of the cover pad 3. The impact energy absorber 4 is composed of a steel sheet which is bent so as to have a U-shaped cross-section and is thinner-walled than a atheretofore conventional one.
The lower ends of the side plates 4b and 4c are bent inwardly. A U-shaped clip 5a is provided at the lower portion of the lower end 4d of the side plate 4b so as to be retained to the peripheral edge of a boss plate 2, and the lower end 4e of the side plate 4c is secured to a retaining piece 6 which is secured to the under surface of the peripheral edge of the cover pad 3 by a screw 8. An adapter piece 9 which is attachable to a support plate 11 through a screw 10 which is secured to the boss plate 2 by a screw 12 is fixed to the retaining piece 6.
The cover pad 3 is so formed as to have a lower rigidity than the impact energy absorber 4 and is composed of a coating layer 3a made of a soft synthetic resin material, and an insert 3b made of a hard synthetic resin material for providing a certain amount of retention of shape for the cover pad 3.
When an impact load is applied in a substantially perpendicular direction to the cover pad 3, since the upper and lower ends of the side plates 4b and 4c of the impact energy absorber 4 are respectively bend inwardly, the deformation of the impact energy absorber 4 takes the form of buckling deformation in which a bending point of each of the side plates 4b and 4c protrudes outwardly, so as to interfere with the inner wall of the side portion 3B of the cover pad 3. Thus, in this steering wheel, impact energy is absorbed by deformation of the impact energy absorber 4, deformation of the cover pad 3 and interference between the cover pad 3 and the impact energy absorber 4 (force for suppressing the deformation of both members, frictional force, and the like).
However, in order to utilize the deformation of the cover pad 3 and the interference action between the cover pad 3 and the impact energy absorber 4 for absorption of impact energy as in this proposal, it is necessary to set the rigidity of the cover pad 3 within a predetermined range, which requires much labor for production of the cover pad 3.